Why aren't center filters built-in?

[Kerry L. Thalmann]

My widest lens at this time is 90mm (on 4x5) and I have no desire for a center filter at this time.

But what if you were to use that same 90mm lens on 5x7? Then you may find a center filter necessary. Yet another reason not to build the center filter into the lens. The 110mm Super Symmar XL is one of my all time favorite lenses. I bought it originally for 4x5, and have used it on that format for years without ever feeling the need for a center filter. Once I began using the same lens on 5x7, and more recently 4x10, I found a center filter absolutely neceesary (for my needs).

Fortunately, it takes the same center filter that I use with my 80mm Super Symmar XL on 4x5. And, yet anopther reason still not to build the center filter into the lens - one filter can be used with multiple lenses.

Kerry

[M Brian Mills]

And one other reason...
I have a Schneider 65mm f8 that was not intended for 4x5 use because the image circle is too small and would have tons of fall-off on the edges, but I use it for 4x5 photomacrography. If I had to adjust my uber-long exposure times to be 2 stops longer because the center filter was on the lens I would have exposures that were upwards of 4-6 hours. Yikes!

[Bob Salomon]

"I would have exposures that were upwards of 4-6 hours. Yikes!"

What aperture are you shooting at now?

[Will Strain]

ah reciprocity multipliers... how I love thee.

[M Brian Mills]

Hey Bob,
I usually shoot wide-open at f8, but use ambient light indoors.
I’m also getting about 10:1 magnification.

[Bob Salomon]

"I usually shoot wide-open at f8, but use ambient light indoors.
I’m also getting about 10:1 magnification."

Then a center filter would not work at all for your application.

But then again if you were using a lens optimized for that magnification and stopped down to it's optimal aperture you would get better results - unless you aren't after the sharpest possible results.